What cleaning and maintenance does a biomass boiler need?

If you are thinking about installing a biomass boiler, you’ll want to know how much cleaning and maintenance is involved.

A biomass boiler needs regular cleaning and servicing as build-ups of ash and clinker can stop it working efficiently and even cause damage. Some of these tasks you will need to do yourself, such as ash emptying and checking. Other tasks, such as the annual service, require extra skills and if you can’t DIY then you’ll need to get a qualified engineer.

It is fair to say that biomass boilers that burn wood logs, chips or pellets, require more day-to-day attention than gas or oil boilers when it comes to cleaning and fuel handling. The amount you’ll have to do depends on which wood fuel you use.

One way to reduce the amount of work you’ll have to do is to make your home as energy efficient as possible. Charlie Baker, SuperHomer from Manchester has had a log gasification boiler since 2007. He says: ‘Make sure you are good with the logistics of fuel supply. Handling the fuel can get really wearing, so retrofit as much energy saving and energy generation kit as you can to your property to reduce heat demand on the boiler and your time in refuelling and cleaning’.

What biomass boiler cleaning will I need to do myself?

You should check that the boiler is working well every day. You will also need to check any automated feed system when filling or at least every week to make sure there are no blockages or unwanted build-ups of fuel.

When it comes to cleaning, the amount of ash produced from good quality wood fuel is generally low. Ash will be mainly found in the combustion chamber, heat exchanger and flue/chimney. If there is no automatic ash cleaning function on your boiler then you will need to clean it and remove the ash yourself. The boiler will need to be shut down and cool before cleaning can take place - depending on your fuel and boiler this could be a weekly task.

If your boiler is self-cleaning then ash from the grate and heat exchanger will automatically be collected in the ash bin so your only cleaning task is emptying it. Some boilers have a mechanism for compressing the ash so you will need to empty the ash bin less often. Depending on the fuel and amount of use the boiler gets this could be relatively infrequent, as little as once a year in some cases. Some boilers have an indicator on the control panel that will let you know when the ash needs to be emptied.

Other than emptying the ash, the amount of work you’ll need to do will depend on which wood fuel you choose. YouGen installer member David Hill of Carbon Legacy describes your three wood fuel options:

“I tell customers that burning logs is a labour of love. It requires daily - sometimes twice daily – loading and ash emptying of the boiler, as well as chopping the wood to size. You’ll also have to make sure you have enough well-seasoned logs ready for burning and store them properly.

Wood chips are generally more suitable for commercial users who have their own wood source. The chips are cheaper to buy than pellets but need more space to store and a bit of effort to keep them in good condition. The boiler will require regular cleaning too.

Wood pellets work very well for domestic customers. A good quality biomass boiler is as maintenance-free as an oil boiler. It just requires an annual service and the ash emptying about once a month. If you don’t want to handle bags of pellets then a boiler automatically fed from a silo is the best option. A blown pellet delivery is as simple as an oil delivery, but a lot less messy.”

There are two other places that will need to be cleaned at least once a year, depending on the type of wood fuel and the amount the boiler is in use:

flue/chimney. You can clean the chimney yourself if you have the skills and equipment, otherwise a qualified sweep is recommended

If you want to minimise the cleaning and maintenance you’ll need to do, it is worth considering the following automated features when selecting a boiler:

Self-cleaning

Ash compression

Control panel or remote indicators for ash emptying or cleaning

Automatic flue cleaning

Automated feeding, with blown fuel delivery (some boilers can be easily adapted to change from manual to automated feeding).

Regular cleaning will save you money. Kate Spohrer, SuperHomer from rural Worcestershire who has had a wood pellet boiler since 2012, explains: ‘Cleaning out the ash and hoovering the grate regularly will save you money by keeping the boiler working efficiently and reducing the cost of replacing corroded parts’.

Before you start cleaning the inside of the boiler, please remember the following safety measures:

ensure the boiler is switched off at the mains

allow it to cool down completely (ideally overnight)

know where the sprung components are and clean carefully.

It’s a dirty job, so wear old clothes and gloves. You might want something comfortable to kneel on, as well as a face mask and eye protection.

What other maintenance will the boiler need?

Manufacturers usually recommend that your boiler is serviced at least once a year. You can DIY, but if you receive the Renewable Heat Incentive (RHI) it is recommended that you maintain the boiler in accordance with the manufacturer’s instructions to ensure maximum efficiency.